Red Cell Distribution Width (RDW) is a measurement included in a routine complete blood count. It assesses the variation in the size of your red blood cells. While a high RDW value can be observed with various health conditions, this article explores the association between elevated RDW and certain types of cancer. This link offers insights into how blood markers can reflect underlying physiological changes.
Understanding Red Cell Distribution Width (RDW)
Red Cell Distribution Width measures anisocytosis, the presence of red blood cells of unequal size. Healthy red blood cells maintain a relatively uniform size, typically ranging from 6.2 to 8.2 micrometers in diameter. The RDW result is expressed as a percentage, indicating how much red blood cell sizes deviate from the average. A normal reference range for RDW in adults is between 11.5% and 15.4%.
An elevated RDW signifies a greater variation in red blood cell sizes. This can arise from several non-cancerous conditions. Common causes include nutritional deficiencies like insufficient iron, leading to iron-deficiency anemia, or a lack of vitamin B12 or folate, often resulting in macrocytic anemia. Chronic conditions such as liver disease, kidney disease, and heart disease can also contribute to an elevated RDW.
Cancers Linked to Elevated RDW
Research indicates an association between elevated RDW and several types of cancer, including both blood cancers and solid tumors. This suggests RDW may reflect systemic changes occurring due to malignancy. The link is an observed correlation, not diagnostic for cancer itself.
Among hematological malignancies, which directly affect the blood and bone marrow, higher RDW values have been noted. Examples include various types of leukemia, such as chronic myeloid leukemia and chronic lymphocytic leukemia. Lymphomas, including diffuse large B-cell lymphoma, and multiple myeloma also show this association. Myelodysplastic syndrome, a group of disorders where blood cells do not mature properly, can also be linked to elevated RDW.
Beyond blood cancers, elevated RDW has been associated with a range of solid tumors. Colorectal cancer is frequently cited, with a strong relationship between high RDW levels and poor overall survival. Lung cancer, including non-small cell lung cancer, and liver cancer (hepatocellular carcinoma) are also linked to increased RDW. Other solid tumors showing this association include breast cancer, renal cell carcinoma, prostate cancer, and cancers of the upper gastrointestinal tract, such as esophageal, gastric, and pancreatic cancers.
The Biological Connection Between High RDW and Cancer
The association between high RDW and cancer stems from several biological mechanisms. Cancer often induces chronic systemic inflammation. This persistent inflammation can disrupt normal red blood cell production, known as erythropoiesis, leading to red blood cells with varying sizes. Inflammatory markers in cancer patients often correlate with increased RDW levels, suggesting RDW may serve as an indirect indicator of this inflammatory environment.
Malignancies and their treatments can also lead to nutritional deficiencies, impacting red blood cell formation. Cancer can cause malabsorption or reduced appetite, resulting in insufficient iron, vitamin B12, and folate. These micronutrients are necessary for the proper development of red blood cells. A deficit in these substances can result in disparate red blood cell sizes, elevating RDW.
Cancer can also directly affect the bone marrow, the primary site of red blood cell production. In blood cancers, or when solid tumors metastasize to the bone marrow, cancer cells can infiltrate and disrupt this environment. This interference can impair the bone marrow’s ability to produce healthy, uniformly sized red blood cells, contributing to anisocytosis and a higher RDW.
High RDW as a Prognostic Indicator
Beyond its association with cancer presence, RDW has shown value as a prognostic indicator in oncology. In diagnosed cancer patients, a high or increasing RDW often correlates with a poorer prognosis. This includes associations with more advanced disease stages, increased metastasis risk, and higher mortality rates. Studies link elevated RDW levels to reduced overall survival, cancer-specific survival, and disease-free survival in various malignancies.
Clinicians can use RDW as part of a broader assessment to monitor disease activity or gauge treatment response. For instance, decreasing RDW levels during therapy might suggest a positive response and an improved outlook. While RDW offers valuable insights, it is a non-specific marker and should always be interpreted by a healthcare professional within the context of a patient’s complete clinical evaluation, other blood test results, and medical history.